feat(groups): backfill participant phone_number from LID-PN mapping - #909

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: mozilla-actions/sccache-action@v0.0.9. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/